DE 20 2010 006 217 U1 discloses a lighting device that is designed for vehicles and that provides a first light emitting unit for generating a first light function and a second light emitting unit for generating a second light function. The second light emitting unit has a flat light guide that has opposing flat sides, to which the input light is passed by a narrow side at the light coupling in face (light input face) in the light guiding direction. The flat light guide has a plurality of light coupling out sections (light output sections) in the light guiding direction; and in these light output sections there are output elements that are arranged on a flat side, which is arranged in the rear seen in the main direction of emission. This arrangement has the effect that the input light that impinges on said output elements is deflected in the direction of the front flat side and can be coupled out at said front flat side. Furthermore, the flat light guide has a plurality of light passage sections, in which no output elements are arranged, so that light radiated from the first light emitting unit can pass through the flat light guide. The rear flat side is assigned a support disk, which has reflecting faces in the light output section, so that the light passing through the rear flat side is reflected back in the direction of the flat light guide and, as a result, is not lost for the second light function. The drawback with this design is that the continuous design of the support plate for the reflecting face causes transmission losses when the first light emitting unit is operating. If the first light emitting unit has an incandescent lamp as the light source, then the result is a higher thermal load.
DE 10 2006 016 656 A1 discloses a lighting device that is designed for vehicles and that comprises a flat light guide having a flat side, which is arranged in the rear seen in the main direction of emission. Said rear flat side has a plurality of output elements that have the effect of deflecting the input light in the direction of the front flat side. These output elements are, as in the case of the aforementioned document, an integral part of the rear flat side.